Process for preparing asymmetrical methine dyes

ABSTRACT

Reaction of pyrazolones and methyleneindolines with orthoformic esters is an advantageous one-step process for preparing asymmetrical methine dyes.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a novel process for preparingasymmetrical methine dyes, to methine dye mixtures, to a process fortheir preparation, and to their use for mass coloration of organicpolymeric materials.

[0002] Asymmetrical methine dyes, for example, the asymmetrical methinedye in Example 1 of this application, are very useful for masscoloration of plastics. Dyes of this kind are prepared, for example, bycondensing the corresponding pyrazolonealdehyde with the corresponding2-methylene-indolenine (cf. DE-B 1,154,894).

[0003] Alternatively, asymmetrical methine dyes may also be prepared bycondensing the corresponding 2-methyleneindolenine-ω-aldehyde withpyrazolone (cf. DE-B 1,172,387 and EP-A 419,110).

[0004] F. Würthner, R. Sens, K.-H. Etzbach, and G. Seybold, Angew.Chemie, 1999, 111 No 11, pp. 1753 to 1757, utilize, for example, aceticanhydride solvent for preparing specific merocyanines.

[0005] C. Reidlinger, R. Dworczak, W. M. F. Fabian, and H. Junck, Dyesand Pigments 24 (1994) pages 185 to 204, utilize not only ethyl acetatebut also acetonitriles as a solvent in the preparation.

[0006] The approaches described above include the disadvantage that atleast one of the two reactant components, preferably the aldehyde, mustfirst be prepared in a further step.

SUMMARY OF THE INVENTION

[0007] There has now been surprisingly found a process for preparingcompounds of the formula (I)

[0008] where

[0009] R¹ is H, halogen (especially Cl, Br, and F), alkyl (especiallyC₁-C₆-alkyl), alkoxy (especially C₁-C₆-alkoxy), nitro, cyano,sulfonamide (especially SO₂NR⁴R⁵), COOH, carboxylic ester (especiallyCOOR⁹, where R⁹ is C₁-C₆-alkyl), or carboxamide (especially CON R⁴R⁵),

[0010] R² is alkyl (especially C₁-C₆-alkyl),

[0011] R³ is alkyl (especially C₁-C₆-alkyl), COOH, carboxylic ester(especially COOR⁹ where R⁹ is C₁-C₆-alkyl), and

[0012] X is H, halogen (especially Cl, Br, and F), SO₂NR⁴R⁵,SO₂N═CH—R⁶R⁷, or SO₂R⁸, where R⁴ to R⁷ are independently hydrogen oralkyl (especially C₁-C₆-alkyl) and R⁸ is alkyl or hydroxyalkyl(especially hydroxyethylene),

[0013] comprising reacting compounds of the formulas (II), (III), and(IV)

[0014] where R¹ and R² are each as defined above for formula (I),

CH(OR)₃   (III)

[0015] where R is C₁-C₆-alkyl (especially methyl), and

[0016] where R³ and X are each as defined above for formula (I), witheach other in the presence of an organic solvent, preferably an organicsolvent selected from the group consisting of dioxane, chlorinatedhydrocarbons, chlorobenzene, dichlorobenzene, toluene, xylene,N-methylpyrrolidone, lower alcohols (such as methanol, ethanol,propanols, butanols, pentanols), and glycols (such as ethylene glycoland diethylene glycol) and the corresponding mono- and dialkyl ethers ofglycols, most preferably n-butanol.

[0017] Organic solvents for the purposes of the present invention arecompounds that do not react with the reaction participants or productsunder the conditions of the condensation reaction.

[0018] In a preferred embodiment of the process according to theinvention, the molar ratio of the compounds (II):(IV):(III) is in therange from 1:1:1 to 1:1.2:2.0, especially in the range from 1:1:1 to1:1:1.3.

[0019] Any symmetrical condensation products (methine dyes) that areformed are easy to remove.

[0020] The process of the invention is preferably carried out at atemperature of 70 to 180° C., especially at 90 to 120° C. For example,the process is carried out under reflux and the resultant alcohol isdistilled off in whole or in part, if appropriate. The process maysimilarly be conducted under superatmospheric pressure in a containedsystem above the boiling point of the solvent used or of at least onereaction component or of the evolving alcohol HOR.

[0021] A condensation reaction for the purposes of this invention isaccordingly a reaction in which alcohol is released.

[0022] The condensation of the invention proceeds without exception evenwithout further additives. Useful catalysts include basic catalysts, forexample, pyridine, piperidine or triethylamine, or acidic catalysts, forexample, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, orcarboxylic acids such as, for example, formic acid, acetic acid, orpropionic acid.

[0023] In a preferred embodiment, about 1 mol of compound (II)(especially 1,3,3-trimethyl-2-methyleneindoline or a derivative thereof)is mixed in butanol with about 1 mol of compound (IV) (especially5-pyrazolone), admixed with about 1.3 mol of trimethyl orthoformate, andheated in the presence or absence of catalyst (especially in thepresence of catalytic amounts of glacial acetic acid) under reflux, withor without distillative removal of methanol, until the components usedhave been converted. This is followed by cooling, filtration, washingwith methanol and water, and drying.

[0024] Preference for use as indolines of the formula (II) is given to1,3,3-trimethyl-2-methyleneindoline, methyl1,3,3-trimethyl-2-methyleneindoline-5-carboxylate,1,3,3-trimethyl-5-chloro-2-methyleneindoline, and1,3,3-triethyl-5-methoxy-2-methyleneindoline. Preference is given tousing 1,3,3-trimethyl-2-methyleneindolines substituted in position 5 bysubstituents such as carboxylic esters, carboxamides, halogen, alkoxy,alkyl, or sulfonamide. Most preference is given to methyl1,3,3-trimethyl-2-methylenindolinecarboxylate.

[0025] Preference for use as compounds of the formula (IV) is given to1phenyl-3-methyl-5-pyrazolone, 1-phenylpyrazolone-3-carboxylic esters,and 1-phenylpyrazolones, preferably those in which the phenyl radical issubstituted by the sulfonyl radical SO₂N═CH—N(CH₃)₂ or SO₂N(alkyl)₂.

[0026] A preferred compound of the formula (III) is methyl orthoformate.

[0027] In a preferred embodiment of the process according to theinvention, the reaction mixture is evaporated to dryness and the dryresidue is then recrystallized from a suitable solvent. Preferably, thereaction mixture is cooled and filtered, and the filter cake is washedwith alcohol and water and subsequently dried.

[0028] The process of the invention preferably provides a productmixture preferably containing

[0029] 90 to 100% (especially 95 to 100%) by weight of the compound ofthe formula (I) and

[0030] 0 to 10% (especially 0 to 5%) by weight of the compound of theformula V.

[0031] The compound of the formula (V) is the symmetrical condensationproduct of the compounds of the formulas (II) and (IV) (2 molequivalents)

[0032] where R³ and X are each as defined above.

[0033] A procedure leading to a particularly high fraction ofasymmetrical compound of the formula (I) is preferably washing thefilter cake of the reaction mixture with alcohols, for example, butanolor methanol. Particular preference is also given to the use of butanolas a solvent during the condensation reaction.

[0034] The invention further provides dye mixtures containing

[0035] 90 to 99.9% by weight of the dye of the formula (I) and

[0036] 0.1 to 10% by weight of the dye of the formula (V).

[0037] The mixture according to the invention likewise has goodproperties when used for the mass coloration of plastics.

[0038] The invention further provides a process for preparing themixture of the invention. This is characterized by the same features asthe process according to the invention for preparing compounds of theformula (I). Preferably, the compounds (II), (III), and (IV) are reactedin little solvent, preferably in 40 to 70% by weight of solvent, basedon the total amount of reactants of the formulas (II), (III), and (IV).Preference is likewise given to washing the resultant filter cake withless methanol. Preference for use as organic solvent for thecondensation reaction is given to glacial acetic acid or glycols.

[0039] The invention accordingly also provides for the use of the dyemixture according to the invention for the mass coloration of plastics.

[0040] The dye mixture according to the invention is very useful for themass coloration of plastics and produces yellowish orange colorations.

[0041] Mass coloration for the purposes of the present invention isespecially a process in which the dye is incorporated into the moltenplastic material, for example, with the aid of an extruder, or in whichthe dye is added to starting components for preparing the plastic, forexample, to monomers prior to polymerization.

[0042] Particularly preferred plastics are thermoplastics, for example,vinyl polymers, polyesters, polyamides, and polyolefins, especiallypolyethylene and polypropylene, or polycarbonates.

[0043] Suitable vinyl polymers include polystyrene,styrene-acrylonitrile copolymers, styrene-butadiene copolymers,styrene-butadiene-acrylonitrile terpolymers, polymethacrylate, andpolyvinyl chloride.

[0044] Also useful are polyesters such as, for example, polyethyleneterephthalates, polycarbonates, and cellulose esters.

[0045] Preference is given to polystyrene, styrene copolymers,polycarbonates, polymethacrylates, and polyamides. Particular preferenceis given to polystyrene, polyethylene, and polypropylene.

[0046] The high molecular weight compounds mentioned may be presentsingly or in mixtures, as plastically deformable compounds or melts.

[0047] The dyes of the invention are preferably used in finely dividedform, for which dispersants may but need not be used.

[0048] When the dye mixture is added after the polymerization, it ispreferably dry mixed or milled with the plastic pellet before thismixture is plasticated and homogenized on mixing rolls or in screws, forexample. However, dyes may also be added to the liquid melt anddispersed therein by stirring until homogeneous. The thus precoloredmaterial is then further processed as usual, for example by spinninginto bristles, filaments, or other spun materials or by extrusion or inthe injection molding process, to form shaped articles.

[0049] Since the dye mixture is stable to polymerization catalysts,especially peroxides, it is also possible to add the dye to themonomeric starting materials for the plastics and then to polymerize inthe presence of polymerization catalysts. To this end, the dye ispreferably dissolved or intimately mixed with the monomeric components.

[0050] The polymers mentioned are preferably colored with the dyemixture of the invention used in amounts from 0.0001 to 1% by weight(especially 0.01 to 0.5% by weight), based on the polymer quantity.

[0051] Pigments that are insoluble in the polymers, for example,titanium dioxide, may be added to obtain corresponding useful hidingcoloration. Titanium dioxide may be used in an amount of 0.01 to 10% byweight (preferably 0.1 to 5% by weight), based on the polymer quantity.

[0052] The process according to the invention provides transparent orhiding brilliant orange colorations having good heat resistance and goodlight, weather and sublimation fastness.

[0053] The process according to the invention may also utilize mixturesof the dye mixture of the formula (I) according to the invention withother dyes and/or organic or inorganic pigments.

[0054] The examples below further illustrate the invention. Theinvention, which is set forth in the foregoing disclosure, is not to belimited either in spirit or scope by these examples. Those skilled inthe art will readily understand that known variations of the conditionsof the following procedures can be used. Parts and percentages are byweight.

EXAMPLES Example 1

[0055] 46.2 g of methyl1,3,3-trimethyl-2-methyleneindoline-5-carboxylate were dissolved in 100ml of n-butanol under nitrogen. 34.8 g of 1-phenyl-3-methyl-5-pyrazolonewere added and stirred in for about 10 minutes. After addition of 22.0 gof trimethyl orthoformate and 1 ml of glacial acetic acid, the mixturewas refluxed (at 102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0056] 78.8 g of a dye that is >98.5% the asymmetrical methine dye ofthe formula 1 below were isolated. The dye gave bold orange masscolorations of plastic (for example, polystyrene). Without glacialacetic acid catalyst, the yield was about 4% lower.

[0057] Recrystallization from butanol afforded the dye of formula 1 inpure form in 97% yield.

Example 2

[0058] Example 1 was repeated using 41.8 g of1-phenyl-3-methyl-5-pyrrolidone and 31 g of methyl orthoformate. 85.9 gof a dye mixture containing about 92% of asymmetrical methine dye of theformula 1 and about 8% of the symmetrical methine dye of the formulabelow were isolated.

[0059] When used for mass coloring plastic (for example, polystyrene),the dye mixture provided a bold orange coloration that, however, isdistinctly yellower than that produced by the dye prepared according toExample 1.

Example 3

[0060] 46.2 g of methyl1,3,3-trimethyl-2-methyleneindoline-5-carboxylate were dissolved in 100ml of n-butanol under nitrogen. 61.6 g of pyrazolone were added andstirred in for about 10 minutes.

[0061] After addition of 22.0 g of tri methyl orthoformate, the mixturewas refluxed at (102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0062] Recrystallization from butanol afforded 100.6 g of the dye of theformula 2 (i.e., 91.6% of theory).

Example 4

[0063] 46.2 g of methyl1,3,3-trimethyl-2-methyleneindoline-5-carboxylate were dissolved in 100ml of ethylene glycol under nitrogen. 37.6 g of pyrazolone were addedand stirred in for about 10 minutes.

[0064] After addition of 22.0 g of trimethyl orthoformate, the mixturewas refluxed (at 102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0065] Recrystallization from butanol afforded 77.0 g of the dye of theformula 3 (i.e., 89.7% of theory).

Example 5

[0066] 46.2 g of methyl1,3,3-trimethyl-2-methyleneindoline-5-carboxylate were dissolved in 100ml of n-butanol under nitrogen. 46.4 g of pyrazolone were added andstirred in for about 10 minutes.

[0067] After addition of 22.0 g of trimethyl orthoformate, the mixturewas refluxed (at 102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0068] Recrystallization from butanol afforded 88.2 g of the dye of theformula 4 (i.e., 93.2% of theory).

Example 6

[0069] 40.6 g of 1,3,3-trimethyl-5-methoxy-2-methyleneindoline weredissolved in 100 ml of n-butanol under nitrogen. 46.4 g of pyrazolonewere added and stirred in for about 10 minutes.

[0070] After addition of 22.0 g of trimethyl orthoformate, the mixturewas refluxed at (102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0071] Recrystallization from butanol afforded 76.5 g of the dye of theformula 5 (i.e., 86.0% of theory).

Example 7

[0072] 41.5 g of 1,3,3-trimethyl-5-chloro-2-methyleneindoline weredissolved in 100 ml of n-butanol under nitrogen. 61.6 g of pyrazolonewere added and stirred in for about 10 minutes.

[0073] After addition of 22.0 g of trimethyl orthoformate, the mixturewas refluxed at (102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0074] Recrystallization from butanol afforded 88.3 g of the dye of theformula 6 (i.e., 84.0% of theory).

Example 8

[0075] 41.5 g of 1,3,3-trimethyl-5-chloro-2-methyleneindoline weredissolved in 100 ml of n-butanol under nitrogen. 56.0 g of pyrazolonewere added and stirred in for about 10 minutes.

[0076] After addition of 22.0 g of trimethyl orthoformate, the mixturewas refluxed at (102 to 105° C.) for 5 hours. A further 3 g of trimethylorthoformate were then added before further refluxing for 10 hours. Thebatch was cooled down with stirring and subsequently stirred for 2hours. It was then filtered by applying a vacuum and the filter cake waswashed with 200 ml of methanol and then with 500 ml of hot water anddried at 80° C. under reduced pressure.

[0077] Recrystallization from butanol afforded 80.1 g of the dye of theformula 7 (i.e., 82.2% of theory).

What is claimed is:
 1. A process for preparing a compound of the formula(I)

where R¹ is H, halogen, alkyl, alkoxy, nitro, cyano, sulfonamide, COOH,carboxylic ester, or carboxamide, R² is alkyl, R³ is alkyl, COOH,carboxylic ester, and X is H, halogen, SO₂NR⁴R⁵, SO₂NCHR⁶R⁷, or SO₂R⁸,where R⁴ to R⁷ are independently hydrogen or alkyl, and R⁸ is alkyl orhydroxyalkyl, comprising reacting compounds of the formulas (II), (III),and (IV)

where R¹ and R² are each as defined above for formula (I), CH(OR)₃  (III) where R is C₁-C₆-alkyl, and

where R³ and X are each as defined above for formula (I), with eachother in the presence of an organic solvent.
 2. A process according toclaim 1 wherein the organic solvent is selected from the groupconsisting of dioxane, chlorinated hydro-carbons, chlorobenzene,dichlorobenzene, toluene, xylene, N-methyl-pyrrolidone, lower alcohols,and glycols and the corresponding mono- and dialkyl ethers of glycols.3. A process according to claim 1 wherein the molar ratio of thecompounds (II):(IV):(III) is in the range from 1:1:1 to 1:1.2:2.0.
 4. Aprocess according to claim 1 carried out at a temperature of 70 to 180°C.
 5. A process according to claim 1 wherein the compound of formula (I)has the formula


6. A mixture comprising 90 to 99.9% by weight of a compound of formula(I)

0.1 to 10% by weight of the compound of the formula V

where R¹ is H, halogen, alkyl, alkoxy, nitro, cyano, sulfonamide, COOH,carboxylic ester, or carboxamide, R² is alkyl, R³ is alkyl, COOH,carboxylic ester, and X is H, halogen, SO₂NR⁴R⁵, SO₂NCHR⁶R⁷, or SO₂R⁸,where R⁴ to R⁷ are independently hydrogen or alkyl, and R⁸ is alkyl orhydroxyalkyl.
 7. A method for mass coloration of plastics comprisingincorporating a mixture according to claim 6 into a plastic.